Leadership plays a signiﬁ cant role in processes of institutionalized cooperation. However, leadership also requires an institutionalized context to be sustainable. It is seldom ad hoc . It rests on continuity, stability, and repetition. Strong leadership seems to be essential for guiding and directing a group of countries towards collective action . Conversely, cooperation between international actors raises questions about how to share both costs and beneﬁ ts, especially when some actors are economically and/or militarily more powerful than others.